Cytomegalovirus is the leading viral cause of congenital disease, often producing serious neurological deficits. CMV attacks the developing central nervous system (CNS) resulting in serious brain disorders that include microencephaly, epilepsy, deafness, microgyria, mental retardation, sensory loss, motor problems, and psychiatric disturbances. In addition, CMV is a clinically important opportunistic virus that can lead to serious neurological disease in AIDS patients. Despite the clinical importance of CMV infections of the brain, relatively little experimental work has been done in this area, and many basic questions remained unanswered. The present application addresses basic mechanisms of viral spread into the brain, and once in the brain, spread by intracellular transport or extracellular diffusion to other brain cells. The hypothesis that CMV can be spread through axonal transport will be studied with in vitro and in vivo models. Although CMV appears to have no absolute host cell preference in the brain, the hypothesis that CMV shows relative cellular preferences will be tested in living brain slices at different developmental ages. A recombinant mouse CMV expressing green fluorescent protein will be used to identify infected cells. Neurons in vitro are all killed by CMV, whereas mature neurons in vivo are protected against CMV. Using a mouse model of immunosuppression, parallel to AIDS, we will test the hypothesis that cell-mediated immunity protects neurons in vivo from CMV proliferation. Neuronal activity plays an important role in establishing the correct circuitry during brain development. The hypothesis that early infection by CMV can generate disturbances in the electrophysiological activity of developing neurons will be tested with whole cell patch clamp recording using current and voltage clamp electrophysiology, and with calcium digital imaging, using primary mouse neuron cultures and brain slices. Virus mediated changes in intracellular ion levels, ion currents, transmitter responses, and membrane properties will be compared in CMV infected and control cells.